Provided by: tcllib_1.19-dfsg-2_all 
NAME
xsxp - eXtremely Simple Xml Parser
SYNOPSIS
package require Tcl 8.4
package require xsxp 1
package require xml
xsxp::parse xml
xsxp::fetch pxml path ?part?
xsxp::fetchall pxml_list path ?part?
xsxp::only pxml tagname
xsxp::prettyprint pxml ?chan?
_________________________________________________________________________________________________
DESCRIPTION
This package provides a simple interface to parse XML into a pure-value list. It also
provides accessor routines to pull out specific subtags, not unlike DOM access. This
package was written for and is used by Darren New's Amazon S3 access package.
This is pretty lame, but I needed something like this for S3, and at the time, TclDOM
would not work with the new 8.5 Tcl due to version number problems.
In addition, this is a pure-value implementation. There is no garbage to clean up in the
event of a thrown error, for example. This simplifies the code for sufficiently small XML
documents, which is what Amazon's S3 guarantees.
Copyright 2006 Darren New. All Rights Reserved. NO WARRANTIES OF ANY TYPE ARE PROVIDED.
COPYING OR USE INDEMNIFIES THE AUTHOR IN ALL WAYS. This software is licensed under
essentially the same terms as Tcl. See LICENSE.txt for the terms.
COMMANDS
The package implements five rather simple procedures. One parses, one is for debugging,
and the rest pull various parts of the parsed document out for processing.
xsxp::parse xml
This parses an XML document (using the standard xml tcllib module in a SAX sort of
way) and builds a data structure which it returns if the parsing succeeded. The
return value is referred to herein as a "pxml", or "parsed xml". The list consists
of two or more elements:
• The first element is the name of the tag.
• The second element is an array-get formatted list of key/value pairs. The
keys are attribute names and the values are attribute values. This is an
empty list if there are no attributes on the tag.
• The third through end elements are the children of the node, if any. Each
child is, recursively, a pxml.
• Note that if the zero'th element, i.e. the tag name, is "%PCDATA", then the
attributes will be empty and the third element will be the text of the
element. In addition, if an element's contents consists only of PCDATA, it
will have only one child, and all the PCDATA will be concatenated. In other
words, this parser works poorly for XML with elements that contain both
child tags and PCDATA. Since Amazon S3 does not do this (and for that
matter most uses of XML where XML is a poor choice don't do this), this is
probably not a serious limitation.
xsxp::fetch pxml path ?part?
pxml is a parsed XML, as returned from xsxp::parse. path is a list of element tag
names. Each element is the name of a child to look up, optionally followed by a
hash ("#") and a string of digits. An empty list or an initial empty element
selects pxml. If no hash sign is present, the behavior is as if "#0" had been
appended to that element. (In addition to a list, slashes can separate subparts
where convenient.)
An element of path scans the children at the indicated level for the n'th instance
of a child whose tag matches the part of the element before the hash sign. If an
element is simply "#" followed by digits, that indexed child is selected,
regardless of the tags in the children. Hence, an element of "#3" will always
select the fourth child of the node under consideration.
part defaults to "%ALL". It can be one of the following case-sensitive terms:
%ALL returns the entire selected element.
%TAGNAME
returns lindex 0 of the selected element.
%ATTRIBUTES
returns index 1 of the selected element.
%CHILDREN
returns lrange 2 through end of the selected element, resulting in a list of
elements being returned.
%PCDATA
returns a concatenation of all the bodies of direct children of this node
whose tag is %PCDATA. It throws an error if no such children are found.
That is, part=%PCDATA means return the textual content found in that node
but not its children nodes.
%PCDATA?
is like %PCDATA, but returns an empty string if no PCDATA is found.
For example, to fetch the first bold text from the fifth paragraph of the body of your
HTML file,
xsxp::fetch $pxml {body p#4 b} %PCDATA
xsxp::fetchall pxml_list path ?part?
This iterates over each PXML in pxml_list (which must be a list of pxmls) selecting
the indicated path from it, building a new list with the selected data, and
returning that new list.
For example, pxml_list might be the %CHILDREN of a particular element, and the path
and part might select from each child a sub-element in which we're interested.
xsxp::only pxml tagname
This iterates over the direct children of pxml and selects only those with tagname
as their tag. Returns a list of matching elements.
xsxp::prettyprint pxml ?chan?
This outputs to chan (default stdout) a pretty-printed version of pxml.
BUGS, IDEAS, FEEDBACK
This document, and the package it describes, will undoubtedly contain bugs and other
problems. Please report such in the category amazon-s3 of the Tcllib Trackers
[http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for enhancements you
may have for either package and/or documentation.
When proposing code changes, please provide unified diffs, i.e the output of diff -u.
Note further that attachments are strongly preferred over inlined patches. Attachments can
be made by going to the Edit form of the ticket immediately after its creation, and then
using the left-most button in the secondary navigation bar.
KEYWORDS
dom, parser, xml
CATEGORY
Text processing
COPYRIGHT
2006 Darren New. All Rights Reserved.